it depends on how wide is the theme’s sidebar. what’s your url so we can have a look? and if you could post the code here would be great too… (use the backtick to insert the code, like using inverted commas. the backtick key is next to the no. 1 key)
i think it didn’t appear because the image is too large. you can adjust the size of your picture by pasting the image code in the editor (in code mode), then in visual mode shrink it until it is small enough for your sidebar. then go back to code mode and copy the image code with the resized details in it.